Editing Advanced Power Management (section)

==APM functions==
There are 21 APM function calls defined that the APM driver can use to query power management statuses, or request power state transitions.<ref name="APM_spec_V12" /> Example function calls include letting the BIOS know about current CPU usage (the BIOS may respond to such a call by placing the CPU in a low-power state, or returning it to its full-power state), retrieving the current power state of a device, or requesting a power state change.

{| class="wikitable"
|- 
! Name !! Code !! Comment
|-
| APM Installation Check  || 0x00 ||
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| APM Real Mode Interface Connect  || 0x01 ||
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| APM Protected Mode 16-bit Interface Connect  || 0x02 || Avoids real or virtual86 mode.
|-
| APM Protected Mode 32-bit Interface Connect  || 0x03 || Avoids real or virtual86 mode.
|-
| APM Interface Disconnect  || 0x04 ||
|-
| CPU Idle  || 0x05 || Requests system suspend.<!--P42--> <BR>0) Clock halted until timer tick interrupt.<BR> 1) Slow clock<!--P29--><ref name="APM_spec_V12" />
|-
| CPU Busy  || 0x06 || Driver tells system APM to restore clock speed of the CPU.
|-
| '''Set Power State'''  || 0x07 || Set system or device into Suspend/Standby/Off state.<!--P44-->
|-
| Enable/Disable Power Management  || 0x08 ||
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| Restore APM BIOS Power-On Defaults  || 0x09 ||
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| Get Power Status  || 0x0A || Supports AC status "On backup power". And battery status.
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| Get PM Event  || 0x0B || Checks for APM events. Shall be called once per second.
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| Get Power State  || 0x0C ||
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| Enable/Disable Device Power Management  || 0x0D ||
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| APM Driver Version  || 0x0E ||
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| Engage/Disengage Power Management  || 0x0F || APM management for a specific device.
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| Get Capabilities  || 0x10 ||
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| Get/Set/Disable Resume Timer  || 0x11 ||
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| Enable/Disable Resume on Ring Indicator  || 0x12 ||
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| Enable/Disable Timer Based Requests  || 0x13 ||
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| OEM APM Installation Check  || 0x80 || Tells if APM BIOS supports OEM hardware dependent functions.
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| OEM APM Function  || 0x80 || Access to OEM specific functions.
|}